Calfo relates to apparatus and a method for replacing the old split-pin assemblies of the guide tubes of a nuclear reactor with new split-pin assemblies. Split-pin assemblies are secured in the flange of the lower guide tube. Each split-pin is held by a nut which penetrates into an upper counterbore in the flange and is seated against the base of the counterbore. During torquing of the nut, the flange on the split pin is drawn into a lower counterbore in the flange of the guide tube and is seated against the top of this counterbore. The replacement is carried out in a robotic work station under a pool of water to prevent exposure of operating personnel to radioactivity. During the replacement operation, the old split-pin assembly is fragmented by metal machining disintegration and the fragments are removed. Following this operation it is necessary to clean the counterbores and the channel between the counterbores. It is an object of this invention to provide a brush tool uniquely suitable for accomplishing this object.
The task of providing an effective brush tool is complicated by the fact that the upper counterbore is not accessible directly from the top; i.e., to cleaning by a brush which is coaxial with the axis of the opening in the guide tube and is inserted in the upper counterbore by vertical movement downwardly. The entrance to the upper counterbore is partially obstructed by the wall of the guide tube which extends upwardly from its flange.
It is an object of this invention to overcome this drawback and to provide a brush tool which shall be capable of effectively cleaning the counterbores in the lower flange of the lower guide tube of a nuclear reactor notwithstanding the obstruction of the part of the tube which extends above the flange.